In some completions it is desirable to control fluid loss into the formation. One way this is done is to have closures over tubular wall openings until the time arrives when such openings need to be operated to allow alternative access through the wall openings. One example of this is when running in a screen assembly with an isolation device. In some applications the access through the screens is closed off inside the string with sliding sleeve valves. These valves later need an intervention to be operated such as a sleeve shifting tool or the sliding sleeves themselves have to be configured to respond to predetermined pressures to operate in a sequence as determined with rupture discs that break at sequentially higher pressures. A mechanical intervention or configuring sleeves to open at predetermined pressures has several disadvantages. The physical intervention takes time that cost money in well downtime and rigs and personnel to accomplish the intervention. Pressure operated sleeves need a piston area to push them to an open position which means the drift diameter of the production string is reduced. Slowing production is costly and can limit the total amount produced from the borehole during its useful life.
The present invention addresses these issues by blocking devices that would otherwise present openings in the wall of the borehole so that fluids can be delivered under pressure to other equipment further down the string or to facilitate circulation or reverse circulation when running in the string or trying to get the string unstuck if it happens to stick when running in. The openings in downhole equipment such as screens can then be opened with a degradable material that goes away with existing or imposed well conditions. Access is then opened through the string through equipment previously sealed to retain internal pressure in the string. Further completion operations can be accomplished or production can begin. Preferably a controlled electrolytic material is used as the material that degrades to open passages through a tubular wall. Controlled electrolytic materials have been described in US Publication 2011/0136707 and related applications filed the same day. The related applications are incorporated by reference herein as though fully set forth. Those skilled in the art will more readily appreciate these and other aspects of the invention from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims.